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Demons in the North Atlantic: Variability of deep ocean ventilation
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  • Graeme Alastair MacGilchrist,
  • Helen Louise Johnson,
  • Camille Lique,
  • David P Marshall
Graeme Alastair MacGilchrist
Princeton University

Corresponding Author:graemem@princeton.edu

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Helen Louise Johnson
University of Oxford
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Camille Lique
Laboratoire d'Océanographie Physique et Spatiale
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David P Marshall
University of Oxford
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Translation of atmospheric forcing variability into the ocean interior via ocean ventilation is an important aspect of transient climate change. On a seasonal timescale, this translation is mediated by a so-called “Demon’ that prevents access to all except late-winter mixed-layer water. Here, we use an eddy-permitting numerical circulation model to investigate a similar process operating on longer timescales in the high-latitude North Atlantic, which we denote the “interannual Demon’. We find that interannual variations in atmospheric forcing are indeed mediated in their translation to the ocean interior. In particular, the signature of persistent strong atmospheric forcing driving deep mixed layers is preferentially ventilated to the interior when the forcing is ceased. Susceptibility to the interannual Demon depends on the location and density of subduction — with the rate at which newly ventilated water escapes its region of subduction being the crucial factor.